Consumption of human milk is associated with reduced incidence and severity of enteric infections, leading to reduced morbidity and mortality in infants. Human milk oligosaccharides (HMO) are known to contribute to this outcome through various mechanisms, including a decoy mechanism and by increasing the growth of beneficial microbes. Increased growth of specific commensals improves the barrier function of the intestinal epithelium and provides spatial competition, reducing pathogen colonization. While several HMO have been successfully synthesized, no large-scale source for the majority of known HMO exists. Large quantities of HMO-like oligosaccharide (OS) are vital for preclinical testing of their antimicrobial functions. Bovine milk contains HMO-like OS (BMO), but they are typically less fucosylated. The fucosylation and sialylation of HMO is important for both direct antimicrobial action via the decoy effect and indirect antimicrobial action via commensal growth enhancement. Low levels of fucosylation and sialylation result in OS with poor specificity of action for growth promotion. During cheese production, whey permeate is produced as a waste by-product, and it contains all of the BMO. We can acquire large quantities whey permeate from industrial cheese manufacturers and isolate the BMO. However, to increase their direct and indirect antimicrobial potency, these OS must be modified to increase their sialylation and fucosylation. By enzymatic modification, we will create a novel class of BMO-based OS with increased antimicrobial activities. First, we will isolate gram to kilogram quantities of OS from bovine milk whey waste streams. Next, we will modify their structures with fucosylation, sialylation, or a combination of both. Finally, we will examine the original and modified OS for antimicrobial actions against several pathogens for decoy action and several commensals for prebiotic specificity. Phase I will demonstrate the feasibility of this approach to generate kilogram quantities of HMO-like antimicrobial OS for preclinical testing.